The slightly ironic thing about finding AR-88s - and I am told lots of HROs - at Bletchley, is that during the war there probably wasn't any of either set on the site.
Bletchley Park was purely involved in decoding the traffic, and the actual receiving of the messages was done elsewhere, with their content being sent to BP by various means, including motorcylce courier I believe. One such receiving station was
Beaumanor Hall in Leicestershire - that being one of many Y-stations around the country tasked with picking up enemy radio traffic.
Richard